Different types of semiconductor components include terminal contacts which provide electrical connection points for applying electronic signals to the integrated circuits contained on the components. For example, bare dice and semiconductor wafers typically include bond pads which function as terminal contacts. Chip scale packages typically include solder balls, which function as terminal contacts. Electronic assemblies, such as circuit boards and field emission displays, can include pads, solder balls or pins which function as terminal contacts.
Typically, an interconnect must be provided for making electrical connections to the terminal contacts on the contacts. For example, semiconductor test systems include an interconnect that makes temporary electrical connections with the terminal contacts on the components. Depending on the system, the interconnect can be die sized, or wafer sized. U.S. Pat. No. 5,686,317 entitled “Method For Forming An Interconnect Having A Penetration Limited Contact Structure For Establishing A Temporary Electrical Connection With A Semiconductor Die”, describes a die level interconnect configured for use with a carrier. U.S. Pat. No. 5,869,974 entitled “Micromachined Probe Card Having Compliant Contact Members For Testing Semiconductor Wafers”, describes a wafer level interconnect configured for use with a wafer prober.
Interconnects are also used to provide permanent electrical connections to a semiconductor component for various electronic assemblies. For example, U.S. Pat. No. 5,578,526 entitled “Method For Forming A Multi Chip Module”, and U.S. Pat. No. 5,789,278 entitled “Method For Fabricating Chip Modules”, describe multi chip modules having interconnects which form permanent electrical connections to the terminal contacts on components.
One material that can be used to fabricate interconnects is silicon. Silicon can be used as a substrate material, and also to form contacts for the interconnect. With silicon, a coefficient of thermal expansion (CTE) of the interconnect matches the CTE of the component. In test systems, the matching CTEs minimize thermal stresses during test procedures, such as burn-in, which are conducted at elevated temperatures. In electronic assemblies, the matching CTEs minimize thermal stresses due to heat generated by the semiconductor component, or by the operating environment.
One aspect of silicon is that it is a semiconductor material, and does not have sufficient electrical conductivity to permit signal transmission. Accordingly, the silicon must be coated with electrically conductive materials to form contacts, conductive traces and bond pads for the interconnect. The conductive materials can include metals, such as copper and aluminum, or metal silicides, such as TiSi2.
Some of the conductive materials used in interconnects do not possess sufficient strength to resist deformation during fabrication or use of electronic assemblies. For example, in test systems, some conductive materials, such as metals, are prone to wear and oxidation with continued usage. Also, some conductive materials, such as metal silicides, do not possess a thermal conductivity which permits efficient heat dissipation from the component.